Picornaviruses as candidate vaccine vectors: Expression of HIV-1 antigens and examination of the effect of HPeV-1 viral 2BC protein on surface MHC-I expression

Picornaviruses generally replicate in the gastrointestinal and respiratory tracts, inducing immunity relevant to sites of exposure. Immune responses elicited by enteroviruses and targeted to mucosal surfaces can have a cellular component in addition to a humoral response. Through careful guidance, these responses could be harnessed as part of a strategy to prevent sexual transmission of the human immunodeficiency virus-1 (HIV-1). We first report the construction and study of replication competent recombinant vectors of coxsackievirus B3 (CVB3) that express one or more portions of the HIV-1 Gag protein. Vectors containing the capsid domain of Gag were initially genetically unstable with protein expression lost after brief passage in tissue culture. Codon modification to increase the G/C content of the HIV-1 capsid sequence resulted in enhanced genetic stability of CVB3 vectors during in vitro passage. Cells infected with a vector expressing the matrix (MA) subunit of the HIV-1 Gag protein were susceptible to lysis by CD8 T cell clones specific for the SL9 epitope found within MA.;We also describe the construction of a replication-competent vector based on HPeV-1. The virus has little intrinsic pathogenicity, and may offer a safe alternative to more virulent expression vectors. Genomic insertions of coding sequences representing an immunodominant cytotoxic T lymphocyte (CTL) HIV-1 epitope, SLYNTVATL (SL9), were retained by the HPeV-1 vector for numerous in vitro passages. Interferon-gamma (IFN-gamma) release from SL9-specific CTL was examined using vector-infected target cells. ELISpot analysis indicated a low, but statistically significant, level of CTL activation occurred.;Modest CTL IFN-gamma release indicated a possible deficiency in presentation of antigen by major histocompatibility complex class I (MHC-I) molecules. These molecules play a crucial role in immune system surveillance and its defense against intracellular pathogens as well as cancer. MHC-I molecules are loaded with peptides from immunoproteosome degraded proteins, which traffic to the cell surface for display to CD8+ T-cells. Viruses may disrupt this pathway during replication, significantly impairing CTL clearance of infected cells. Our data revealed differences in disruption of the secretory pathway during viral replication between CVB3 and HPeV-1. Variances in this virus family include differences in site of replication and receptor usage. Understandably, they may also vary in disruption of cellular processes. HPeV-1 2BC protein disruption of class 1 presentation, previously unknown, was compared to the more studied picornavirus CVB3.;These data show the potential for utilizing HPeV-1 and CVB3 as a CTL epitope vector, although effective immunogenicity will require enhancement of antigen presentation, possibly through mutation of the 2BC protein.